Genetic Variability, Heritability, and Trait Association Analysis of Physiological and Morphological Traits in Iraqi Rice (Oryza sativa L.) Genotypes

Abstract

Assessing genetic diversity and trait relationships is essential for identifying useful selection criteria in rice breeding. In this study we looked at genetic variability, broad sense heritability, genetic advance, and also how traits relate to each other, focusing on some selected physiological and morphological characteristics across five Iraqi rice, Oryza sativa L. genotypes. A field trial was carried out under a randomized complete block design with three replications, during the 2025 summer season in Wasit Governorate, Iraq. Chlorophyll content, flag leaf length, flag leaf width, leaf area, plant height, and number of tillers were noted at heading to flowering stage, 113 days after sowing. The variance analysis, showed significant to very significant differences among genotypes for every trait we measured, which suggests there was a clear and measurable phenotypic variation inside the materials that were tested. Analysis of variance showed significant to highly significant differences among genotypes for all traits examined, so it looks like there is clear phenotypic variation across the materials that were tested. The Local Amber genotype managed to record the highest mean values for chlorophyll SPAD, flag leaf dimensions, leaf area, plant height, and number of tillers, all within this particular environment. Broad-sense heritability was from 71.93% for flag leaf length up to 96.32% for number of tillers, but genetic advance as a percentage of the mean was top for number of tillers and leaf area. Overall, these outcomes point that number of tillers and leaf area may be more responsive to selection in the tested genotypes. Pearson correlation analysis then indicated positive relationships among essentially all measured traits, and especially strong links were observed between leaf area and flag leaf width, plant height, and number of tillers. Overall, the findings provide preliminary evidence of useful variability among Iraqi Amber-type rice genotypes and suggest that leaf area and tiller number may serve as potential indirect selection indicators. Further multi-location and multi-season studies including grain yield are recommended to confirm their breeding value.